c_cpp 127.单词阶梯

Posted 2021-05-14

class Solution {
public:
    int ladderLength(string beginWord, string endWord, vector<string>& wordList) {
        unordered_set<string> dict(wordList.begin(), wordList.end());
        queue<string> Q;
        int res = 1;
        Q.push(beginWord);
        
        while (!Q.empty()) {
            int n = Q.size();
            for (int i = 0; i < n; i++) {
                string curStr = Q.front(); Q.pop();
                if (curStr == endWord) return res;
                for (int j = 0; j < curStr.size(); j++) {
                    string curStr_c = curStr;
                    for (int k = 0; k < 26; k++) {
                        curStr_c[j] = 'a' + k;
                        if (dict.count(curStr_c)) {
                            Q.push(curStr_c);
                            dict.erase(curStr_c);
                        }
                    }
                }
            }
            res++;
        }
        
        return 0;
    }
};